The Section works on the molecular interaction between antigens and monoclonal antibodies. Elucidation of the nature of this interaction is important not only in immunology, but for a general understanding of how receptors and haptens work. Our approach is threefold (see below, A, B, and C.). In addition we are working on development of antibodies against possible epitopes on glycoprotein envelopes of viruses (D). A. The interaction of ligands, both natural and synthetic, with monoclonal antibodies is evaluated and correlated with epitopes on both the antigen and the protein. B. Rearranged immunoglobulin genes are cloned with the object of obtaining defined mutations of antibodies by oligonucleotide- directed mutagenesis in order to study the particular contribution to binding by certain amino acid residues in the antibody. C. The labeling of immunoglobulins is effected by their reaction with specifically designed derivatives of ligands. D. Synthetic carbohydrate determinants which are part of glycoproteins are derivatized and linked to protein carriers. Antibodies obtained to these immunogens are then obtained, purified and evaluated for their possible binding to known glycoproteins and viruses.